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sdl: fix touchscreen input on hosts without native touch support #938

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sdl: fix touchscreen input on hosts without native touch support #938

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30 changes: 28 additions & 2 deletions src/input/sdl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -432,6 +432,12 @@ static void remove_gamepad(SDL_JoystickID sdl_id) {
void sdlinput_init(char* mappings) {
memset(gamepads, 0, sizeof(gamepads));

// Touch is handled above, either natively or by emulating the mouse there.
// Letting SDL also synthesise mouse events from touch moves its internal
// cursor, and the compositor then re-reports the real pointer once the touch
// ends, which arrives as a large spurious motion.
SDL_SetHint(SDL_HINT_TOUCH_MOUSE_EVENTS, "0");

SDL_InitSubSystem(SDL_INIT_GAMECONTROLLER);
#if !SDL_VERSION_ATLEAST(2, 0, 9)
SDL_InitSubSystem(SDL_INIT_HAPTIC);
Expand Down Expand Up @@ -542,8 +548,28 @@ int sdlinput_handle_event(SDL_Window* window, SDL_Event* event) {
event->tfinger.x = SDL_max(SDL_min(1.0f, event->tfinger.x), 0.0f);
event->tfinger.y = SDL_max(SDL_min(1.0f, event->tfinger.y), 0.0f);

LiSendTouchEvent(touchEventType, event->tfinger.fingerId, event->tfinger.x, event->tfinger.y,
event->tfinger.pressure, 0.0f, 0.0f, LI_ROT_UNKNOWN);
if (LiSendTouchEvent(touchEventType, event->tfinger.fingerId, event->tfinger.x, event->tfinger.y,
event->tfinger.pressure, 0.0f, 0.0f, LI_ROT_UNKNOWN) == LI_ERR_UNSUPPORTED) {
// The host has no native touch support, so drive the mouse instead.
int w, h;
SDL_GetWindowSize(window, &w, &h);

// A touchscreen is absolute, so position the pointer where the finger is
// rather than following the mouse capture mode.
switch (event->type) {
case SDL_FINGERDOWN:
LiSendMousePositionEvent(event->tfinger.x * w, event->tfinger.y * h, w, h);
LiSendMouseButtonEvent(BUTTON_ACTION_PRESS, BUTTON_LEFT);
break;
case SDL_FINGERMOTION:
LiSendMousePositionEvent(event->tfinger.x * w, event->tfinger.y * h, w, h);
break;
case SDL_FINGERUP:
// Deliberately no movement here: a release carries no new position.
LiSendMouseButtonEvent(BUTTON_ACTION_RELEASE, BUTTON_LEFT);
break;
}
}
break;
case SDL_CONTROLLERAXISMOTION:
gamepad = get_gamepad(event->caxis.which, false);
Expand Down